JP4615765B2 - Optical deflector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical deflector that deflects laser light by rotating a rotating body formed by a rotating polygon mirror.
[0002]
[Prior art]
JP-A-11-271654 is known as a known technique of an optical deflector. An object of the publication is to provide a polygon scanner that performs high-definition image formation by reducing the windage loss of a polygon mirror on which a plurality of laser beams are incident. As shown in FIG. In the polygon scanner 30, the fixed shaft 33 is inserted into the hollow of the rotating sleeve 37, and the flange 38 fixed to the rotating portion 39 of the magnetic bearing and the polygon mirror 40 are fixed to the rotating sleeve 37, and these constitute a rotating body 45. To do. The magnetic bearing rotating portion 39 is inserted into a permanent magnet assembly 34 embedded in the upper end recess of the fixed shaft 33, and the fixed shaft 33 moves the rotating sleeve 37 in the axial direction by the magnetic bearing rotating portion 39 and the permanent magnet assembly 34. When the rotating sleeve 37 is rotated and supported, the rotating sleeve 37 is supported in the radial direction by the dynamic pressure of air with the contact surface with the rotating sleeve 37 as a dynamic pressure air bearing surface. The polygon mirror 40 is formed with mirror surface portions 40a and 40b and a non-mirror surface portion 40c, and the non-mirror surface portion 40c is formed with a smaller diameter than the mirror surface portions 40a and 40b, thereby reducing weight and reducing windage loss at high speed rotation. It has been made. Accordingly, it is possible to stably rotate at high speed with low vibration and to form a high-definition image.
[0003]
[Problems to be solved by the invention]
However, in the conventional example, the airflow generated by the rotation of the rotating body is disturbed in the constricted portion of the rotating body, particularly around the non-mirror surface portion 40c between the mirror surface portions 40a and 40b. As a result, windage loss increases and the power consumption of the motor increases. In addition, the rotational speed unevenness of the motor increases, and the scanning jitter of the laser beam increases. There is a problem that noise increases due to turbulent flow around the mirror.
[0004]
The present invention regulates the airflow generated around the rotating body by rotating the rotating body, prevents turbulence, suppresses windage loss, reduces motor power consumption, suppresses motor rotation speed unevenness, An object of the present invention is to provide an optical deflector that reduces the beam scanning jitter and further reduces the noise level caused by wind-off around the mirror.
[0005]
In addition to preventing the reflecting surface of the rotary polygon mirror from being damaged by the rectifying member during assembly, the rectifying member generates heat generated by the rotation of the rotating body in addition to facilitating the manufacture of the rectifying member having a unique shape. An object is to provide a highly reliable optical deflector by absorbing and radiating heat.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, a rotating body formed by a rotating polygon mirror is rotated, and a rectifying member that arranges an air flow generated by the rotation of the rotating body is arranged around the rotating body. An optical deflector for deflecting laser light, wherein two or more rotating polygonal mirrors are formed on the rotating body, and the rectifying member is interposed between at least one adjacent rotating polygonal mirrors . Is the most important feature.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 is an overall cross-sectional view of an optical deflector according to a first embodiment of the present invention, FIG. 2 is an exploded perspective view of the housing, printed circuit board, and upper and lower components of FIG. 1, and FIG. 3 is a rectifying member of FIG. FIG.
[0014]
An attachment reference surface 1a to the optical housing is formed on the lower surface of the housing 1. A bearing mounting portion 1b is formed at the center of the upper surface of the housing 1, and a fixed shaft 2 constituting a dynamic pressure air bearing is fixed. A groove 2a for forming a dynamic pressure air bearing is formed on the cylindrical surface of the fixed shaft 2. When the rotating body 3 that is a rotating polygon mirror starts rotating, the air pressure in the bearing clearance formed between the rotating sleeve 15 and the fixed shaft 2 increases and supports the rotating body 3 in the radial direction (radial direction) without contact. .
[0015]
A fixed portion 5 of an attraction type magnetic bearing is fixed inside the fixed shaft 2. The fixed portion 5 of the attraction type magnetic bearing is fixed by being sandwiched in the axial direction by press-fitting and fixing the cap member 6 and the stopper 7 to the inner cylinder portion of the fixed shaft 2. A fine hole having a diameter of about 0.2 to 0.5 is formed in the central portion of the cap member 6 to attenuate the vertical vibration using the viscous resistance when air passes. Both the cap member 6 and the stopper 7 are made of a non-magnetic material such as a stainless steel plate.
[0016]
The fixed portion 5 of the attraction type magnetic bearing is made of a ferromagnetic material in which a ring-shaped permanent magnet 8 magnetized in two poles in the rotation axis direction and a central circle smaller than the inner diameter of the ring-shaped permanent magnet 8 are formed. 1 fixed yoke plate 9 and a second fixed yoke plate 10 made of a ferromagnetic material having a central circle smaller than the inner diameter of the ring-shaped permanent magnet 8. The first fixed yoke plate 9 and the second fixed yoke plate 10 sandwich the ring-shaped permanent magnet 8 in the axial direction, and the center circle of the first fixed yoke plate 9 and the center circle of the second fixed yoke plate 10 are Arranged and fixed so as to be coaxial with the rotation center axis. As a material of the ring-shaped permanent magnet 8, a rare earth permanent magnet is mainly used. Steel plates are used for the fixed yoke plates 9 and 10. The fixed shaft 2 is made of a nonmagnetic material such as ceramic or aluminum alloy.
[0017]
On the upper surface of the housing 1, a printed circuit board 11 having a hole formed in a substantially central portion is disposed. A printed circuit board 11, a spacer 12, and a stator core 13 around which a motor winding 13a is wound are sequentially fitted to the outer diameter of the bearing mounting portion 1b of the housing 1, and the tip of the bearing mounting portion 1b is caulked (plastic deformation). 3 parts are sandwiched and fixed.
[0018]
A radial gap / outer rotor type brushless motor is configured in which a rotor magnet 14 attached to the rotating body 3 and a stator core 13 around which a motor winding 13a is wound face each other in a direction perpendicular to the rotation axis. In the rotating body 3, a metal outer peripheral member 16 mainly composed of aluminum is fixed to the outside of the ceramic rotating sleeve 15 by shrink fitting over the entire axial length of the rotating sleeve 15, and a mirror portion 16a is integrally formed. ing. A rotor magnet 14 for a motor is adhered or press-fitted and fixed to the lower side of the outer peripheral member 16.
[0019]
A closing member 17 having a linear expansion coefficient substantially equal to that of the outer peripheral member 16 is press-fitted and fixed in the through hole at the upper end of the outer peripheral member 16. The closing member 17 has a disk shape. A rotation part 18 of an attraction type magnetic bearing is disposed and fixed to the closing member 17. An outer cylindrical surface that forms a magnetic gap is formed between the central circle of the first fixed yoke plate 9 and the central circle of the second fixed yoke plate 10 on the rotating portion 18 of the attractive magnetic bearing. It arrange | positions so that a cylinder surface may become coaxial with a rotation center axis | shaft. A permanent magnet or a steel-based ferromagnetic material is used for the rotating portion 18 of the attractive magnetic bearing.
[0020]
Balance correction is performed on the correction surfaces of the upper and lower parts of the rotating body 3 so that the unbalanced vibration becomes a very small level. The printed circuit board 11 is pattern-wired to the motor winding 13a and the hall element 11a and energizes the motor winding 13a sequentially according to the position detection signal of the hall element by a drive circuit provided integrally or separately. Switching is performed to rotate the rotating body 3 to perform constant speed control.
[0021]
Rectifying members 19 and 20 are disposed above the housing 1 and the printed circuit board 11 so as to surround the rotating body 3. Further, a cover 21 is fixed to the housing 1 with screws so as to surround and sandwich the rectifying members 19 and 20. The cover 21 has an opening for entering and exiting laser light, and the glass window 22 is sealed with a double-sided tape or an adhesive.
[0022]
The rectifying members 19 and 20 have a structure divided into two in the rotation direction. By combining two parts from the left and right of the rotating body 3, the rectifying members 19 and 20 are also provided on the constricted portion of the rotating body 3. Projecting portions 19a and 20a are arranged to prevent turbulent flow from occurring in the constricted portion of the rotating body 3. The facing surfaces 19b and 20b of the rectifying members 19 and 20 facing the mirror portion 16a of the rotating body 3 are arranged and formed at substantially equal positions in the vertical direction, and the airflow generated above and below the mirror becomes unbalanced. , Preventing the occurrence of turbulence. Moreover, the opposing surfaces 19c and 20c of the rectifying members 19 and 20 that oppose the outer peripheral surface of the rotating body 3 are formed in a cylindrical shape except for the laser light incident / exit portion, and flow airflow generated at the outer peripheral portion. This prevents the occurrence of turbulent flow at the outer periphery.
[0023]
By arranging the rectifying members 19 and 20 around the rotating body 3, adjusting the airflow around the rotating body and preventing the turbulent flow, the windage loss is reduced and the power consumption is reduced. Unevenness of motor rotation speed is reduced and scanning jitter is reduced. In addition, the noise level due to wind cuts around the mirror is reduced.
[0024]
If the rectifying members 19 and 20 are formed of a resin material, the mirror surface is not damaged even if the rectifying members 19 and 20 are assembled from the left and right sides of the rotating body during assembly even if they contact the mirror portion 16a of the rotating body 3. Moreover, the rectifying members 19 and 20 having a complicated shape can be easily manufactured by molding. Further, if the rectifying members 19 and 20 are made of a material having high thermal conductivity such as aluminum die cast, heat generated by air friction around the mirror is absorbed and radiated from the rectifying members 19 and 20 so that the rotating body can be made efficient. It can cool well. As a result, it is possible to prevent the deterioration of the mirror flatness due to the temperature rise of the rotating body 3.
[0025]
4 is an overall sectional view of an optical deflector according to a second embodiment of the present invention, FIG. 5 is an exploded perspective view centering on the rectifying member of FIG. 4, and FIG. 6 is a sectional view of the rectifying member of FIG. is there. The second embodiment is different from the first embodiment in that the rotating body 3 has a two-stage mirror configuration. Description of the same parts as those in the first embodiment is omitted.
[0026]
The protrusions 42a and 43a of the rectifying members 42 and 43 are arranged in the constricted part between the two-stage mirrors 41a and 41b, thereby preventing turbulence from occurring in the constricted part between the mirrors. The facing surfaces 42b, 43b of the rectifying members 42, 43 facing the mirror portion of the rotating body 3 are arranged and formed at substantially equal intervals in the vertical direction, and the airflow generated above and below the mirror becomes unbalanced, It prevents turbulent flow. Further, the facing surfaces 42c and 43c of the rectifying members 42 and 43 facing the outer peripheral surface of the rotating body 3 are formed in a cylindrical shape except for the laser light incident / exit portion, and flow airflow generated in the outer peripheral portion. This prevents the occurrence of turbulent flow at the outer periphery.
[0027]
Although the embodiment according to the present invention has been described above, the present invention relates to an optical deflector in which a rectifying member is disposed around a rotating body. Configurations such as a bearing system and a motor system are not limited to the present embodiment.
[0028]
【The invention's effect】
According to the first aspect of the present invention, by adjusting the air flow generated around the rotating body by the rotation of the rotating body and preventing the turbulent flow, the windage loss can be suppressed and the power consumption of the motor can be reduced. In addition, it is possible to reduce unevenness in the rotation speed of the motor and reduce the scanning jitter of the laser beam. Furthermore, it is possible to reduce the noise level due to wind cutting around the mirror. And the turbulent flow between a rotating polygon mirror and a rotating polygon mirror can be prevented.
[Brief description of the drawings]
FIG. 1 is an overall sectional view of an optical deflector according to a first embodiment of the present invention.
FIG. 2 is an exploded perspective view of the housing, the printed circuit board, and the upper and lower components of FIG.
FIG. 3 is a cross-sectional view of the rectifying member in FIG. 1;
FIG. 4 is an overall cross-sectional view of an optical deflector according to a second embodiment of the present invention.
5 is an exploded perspective view centering on the rectifying member of FIG. 4; FIG.
6 is a cross-sectional view of the rectifying member in FIG. 4;
FIG. 7 is an overall cross-sectional view of an optical deflector according to a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Housing 3 Rotating body 11 Printed circuit board 19, 20 Rectification member

Claims (1)

In an optical deflector for deflecting a laser beam in which a rotating body formed by a rotating polygon mirror is rotated, and a rectifying member for arranging an air flow generated by the rotation of the rotating body is arranged around the rotating body ,
An optical deflector, wherein two or more rotary polygon mirrors are formed on the rotary body, and the rectifying member is disposed between at least one adjacent rotary polygon mirror .

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